This invention relates to a hinge assembly for an access door or lid or cover or the like.
The hinge assembly of the present application is particularly useful on access doors which, when opened, are intended to remain in the open position and not swing shut, or which, when raised, will remain in the raised position and not fall down.
In my prior U.S. Pat. No. 4,490,884, an adjustable friction hinge assembly is shown made preferably of thermoplastic material and comprising a first hinge leaf having a pair of spaced-apart non-adjustable knuckles having noncircular, preferably hexagonal, through holes, and a second hinge leaf having a single adjustable knuckle which fits into the space between the spaced-apart non-adjustable knuckles and forms the middle knuckle of a three-knuckle hinge. The middle knuckle has a wrap-around portion and a pair of extensions therefrom. The inside diameter of the middle knuckle is adjustable and the adjustment is controlled by an adjustment screw which controls the spacing between the middle-knuckle extensions. By these means, the frictional torque resistance of the middle knuckle on the hinge pin in controlled. Provision is made for squeezing some of the plastic material of one of the middle-knuckle extensions into the threads of the adjustment screw, thereby to maintain the adjustment at its initially set position despite repeated openings and closings of the lid.
In a preferred embodiment, the opposite end portions of the hinge pin are hexagonal in cross-section and have a maximum diameter which is larger than the diameter of the central portion of the hinge pin which has a smaller circular cross-section. The maximum diameter of the hexagonal end portions is also larger than the inside diameter of the adjustable middle knuckle. Thus, in the embodiment shown in my U.S. Pat. No. 4,490,884, the hinge pin is shown in two segments, an upper segment and a lower segment, and insertion of the hinge pin into the hinge knuckles is accomplished by inserting the smaller circular portions of the two segments into the hinge knuckles from opposite ends. The two segments are held together by a pin positioned in one of the circular portions which is received within an axial hole in the other circular portion.